Cognitive Radios In TV White Spaces

Transcription

1 Cognitive Radios In TV White Spaces Monisha Ghosh Philips Research North America November 2 nd, 2007 Outline White Spaces : what, why and when Cognitive Radio: applications to TV white spaces. Technical Challenges: Sensing and Protocols Industry initiatives: IEEE & White Space Coalition Philips involvement Conclusions 2 1

2 Spectrum Occupancy And Recent FCC Activity AM/FM Radio TV Wireless industry forms a small part of the spectrum Cellular bands: ~250 MHz ISM Band: 80 MHz MHz 1 GHz 2 GHz 3 GHz Task Force reports NPRM on Cognitive Radios NPRM on 3.6 GHz Proposed Rulemaking NPRM on TV bands 3 White Spaces In TV Bands 1. Intro What are white spaces? Gaps in frequency-band that will be available when broadcasters give back their analog frequency allocation. Why are they useful? TV frequencies have excellent propagation characteristics Well suited for long-range wireless networks. Potential Applications: Rural broadband access. When will it be available? February 17, 2009: when transition to digital is complete. Source: New America Foundation 4 2

3 Availability of White Spaces In TV Bands Enormous benefits especially for rural areas. Unlicensed usage of these bands could lead to an explosion of new applications. Source: New America Foundation 5 1. Intro Cognitive Radio Cognitive radio = flexible re-configurable radio ( quickly adapts transmission characteristics ) + smarts ( aware of spectrum usage in vicinity, 1makes intelligent decisions on that basis, and reacts to evolving FCC policies ) Spectrum white spaces (unused TV channels) time TX power multicarrier transmissions in unused TV channels 2 Non-contiguous transmissions 6 MHz TV channel frequency [MHz] 6 3

4 Incumbents and Spectrum Sensing Incumbents in TV bands: TV broadcasting, using 6 MHz channels (primary users). Wireless microphones, regulated by Part 74, using 200 khz bandwidth (licensed secondary). Spectrum Sensing Periodically and dynamically monitors spectrum to determine availability for use by unlicensed devices on a non-interfering basis. Availability determined by incumbent signal level falling below a predetermined sensing threshold : dbm for TV (30 db below threshold of visibility). Incumbents have to be protected at all costs 7 Industry Initiatives: (a) IEEE IEEE PAR: develop a standard for a cognitive radiobased PHY-MAC interface for use by license-exempt exempt devices on a non-interfering basis in spectrum that is allocated to the TV Broadcast Service. Wireless Regional Area Network (WRAN): range: km, data rates 4 20 Mbps. Professionally installed, fixed CPEs. Started in 2005, due for completion in Broadcasters as well as equipment providers involved. 8 4

5 Industry Initiatives: (b) White Space Coalition Companies: Philips, Microsoft, Google, Dell, Intel etc. Objective: Petition FCC to allow the use of personal/portable devices in the TV white spaces. Applications: whole-home coverage for video streaming etc. Status: 2 prototype devices submitted to FCC for testing, one by Microsoft and one by Philips. Results for Philips: The test results verify the ability of the prototype to reliably detect television channels occupied with DTV signals down to the specified level of -114 dbm. OET report, July 31, Ongoing field tests to demonstrate sensing ability 9 Philips Involvement Active participant in IEEE : working draft based on Philips proposal. Key player in the White Space Coalition: only prototype device tested thus far to meet or exceed specified sensing thresholds. Awarded the following: 10 5

6 Conclusions TV White Spaces offer an unprecedented opportunity to test new spectrum polices that will change the way future spectrum is allocated. Move away from the existing licensed/unlicensed split to more flexible spectrum use. Evolving cognitive radio technology will enable new applications to utilize the increased available spectrum in an optimal way. Match radio resources to application needs. Better interference management. 11 6